1. Field
The present invention relates to a method and system for detecting a presence of a block heater in an automobile.
2. Description of the Related Art
In a conventional automobile, a block heater is an accessory used to heat an engine block, in geographic regions with cold temperatures. Heating the engine block can ease starting an engine. However, heating the engine block with a block heater generally raises an engine coolant temperature (“ECT”) of coolant to a much greater extent than an intake air temperature (“IAT”) of intake air used for combustion in the engine. This results in a temperature differential between the IAT and the ECT.
This temperature differential can result in the false detection of a malfunction by the engine control unit (ECU). Under normal conditions, i.e. without the use of a block heater, the ECT and the IAT normalize towards each other after a relatively long soak time of 7 hours with the engine off as seen in FIG. 1. Taking advantage of this characteristic, a malfunction is detected when the ECT-IAT is not in the specified range after a 7 hour soak. In FIG. 1, a curve 134 represents the ECT, while a curve 136 represents the IAT. As can be seen, the ECT and the IAT gravitate towards each other after 7 hours of soak time as indicated by arrows 164. However, when a block heater is used, the ECT and the IAT diverge. Therefore, to prevent detection of a diagnostic trouble code (which indicates an engine malfunction), a presence of a block heater must be detected.
Conventional methods for determining engine malfunctions have tried to determine the presence of the block heater by checking for a temperature difference in the ECT after a period of time. For example, as seen in FIG. 2, one conventional method of determining whether a block heater exists includes taking a temperature difference of the ECT from the start of the engine and at some time afterwards. In FIG. 2, a curve 138 represents an ECT for a first automobile and a curve 140 represents an ECT for a second automobile. As can be seen, in both situations, after 10 seconds, there is a temperature difference in the ECT from the start of the engine and after 10 seconds has lapsed. When the temperature difference is sufficiently large such as 3° C., this indicates that there is a block heater. The conventional methods are dependent on the relative position of the ECT sensor relative to the block heater.
However, these conventional methods can be inadequate depending on the configuration of the automobile and/or the placement of the block heater. For example, in some automobiles, depending on the placement of the ECT sensor, the ECT actually rises before falling and then rises again. This can occur, for example, when the block heater raises the temperature of the coolant used to cool the engine, and which are stagnant near the engine when the engine is off. When the engine is started, the coolant circulates through the engine and radiator hoses, and the ECT sensor initially comes into contact with the coolant that was stagnant near the engine, and which has been warmed by the block heater, resulting in an increase in the ECT. As the coolant further circulates, coolant which was not warmed by the block heater comes into contact with the ECT sensor, lowering the ECT detected by the ECT sensor. As the engine is fully operational, the ECT again begins to rise.
This can be seen, for example, in FIG. 3, the curve 142 represents the ECT for a third automobile and the curve 144 represents the ECT for a fourth automobile. A curve 146 represents an automobile without a block heater. In such a situation, after 10 seconds, the temperature difference from the ECT at the start of the engine to the ECT at 10 seconds is small, such as 1° C. Using the conventional method, this would indicate that the block heater was not present, and can result in a false indication of an engine malfunction.
Thus, there is a need for a method and system for detecting a presence of a block heater in an automobile.